But, this is not enough, 1 more step is needed for this setup to work:

This one is quite obvious but there is a catch.

All the ports in port-channel need to have same native vlan. And here is the catch, since it is 801q VLAN trunk, you can’t use a 801q VLAN as native VLAN. So as soon as you set a native vlan not part of 801q tagging, you would be able to see all interfaces in lacp trunk in Big IP.